Systems have been proposed in which a support slideway enabling the leaf to slide with respect to the opening is furthermore capable of being moved transversely to the opening via arms in order to ensure the inserting and extracting movement of the leaf with respect to the opening at the end of the closing movement and at the beginning of the opening movement respectively. The slideway must be very robust in order to support the weight of the leaf which is cantilevered toward the rear when it is in the open position. The slideway is therefore heavy, the weight supported by the arms during the insertion and the extraction is therefore great, and the device is heavy and expensive. Moreover, the slideway necessarily has such a limited length that it can be reinserted into the opening when the leaf finishes its closing travel. This limits the travel of the slide-way to such an extent that it is generally necessary to double the slideway, in other words to provide a slideway with two telescopic stages so that the leaf clears the opening sufficiently when it is in the open position. This makes the slideway even heavier and further aggravates the problems mentioned above. Furthermore, whether the slideway is in a single stage or two telescopic stages, the arms ensuring the inserting the extracting movement of the leaf may be parallel plunger systems, or else parallel connecting rods forming a deformable parallelogram with the slideway and with the frame of the opening. In both case, the leaf always remains parallel to itself. Thus, the leaf cannot be given certain particular trajectories which are desirable in practice such as the so-called "oscillating" trajectory.
In order to ensure the so-called "oscillating" trajectory, FR-A-2,621,879 discloses a device comprising means for selectively spacing-apart the leaf from the rear edge of the opening, in other words the edged toward which the leaf is displaced during its opening movement. The selective spacing-apart means are associated with two coaxial drive pinions which mesh with two racks, one of which extends along the upper edge and the other of which extends along the lower edge of the leaf. The selective spacing-apart means are also associated with a roller which supports the weight of the leaf in the vicinity of its upper edge, and with rollers which position the leaf laterally in the vicinity of its upper and lower edges. The leaf carries, in the vicinity of its front edge (relative to the closing direction), in other words its edge remote from the selective spacing-apart means when it is in the closed position, an upper roller and a lower roller which follow tracks integrally connected to the frame of the opening and thus contribute toward the lateral positioning of the leaf. These tracks defined the trajectory of the front edge of the leaf, in particular in the vicinity of the closed position. The trajectory of the rear edge of the leaf in the vicinity of the closed position is defined by the selective spacing-apart means. The leaf can therefore assume oblique positions with respect to the plane of the opening. The leaf is prevented from tilting about axes perpendicular to the plane of the opening as the two pinions are coupled rigidly to each other.
It is, however, costly, relatively complex and of a relatively great size along the whole length of the rear edge of the opening. This device also has the disadvantage of requiring racks on the inner face of the leaf.